Device for Evaporating a Volatile Material

ABSTRACT

An assembly for evaporating a volatile material is described, the assembly comprising a device and a refill which are detachable from one another: wherein the device comprises a magnetic induction coil configured to operate with an alternating current passed therethrough at a frequency of between substantially 20 KHz to substantially 500 KHz and one or more volatile fluid emanation channels containing at least one piece of heat-conducting, non-magnetic metal foil and/or deposited heat-conducting, non-magnetic metal; and wherein the refill comprises at least one magnetic susceptor having a coercivity of substantially 50 ampere/metre (H c ) to substantially 1500 ampere/metre (H c ) and a substantially liquid-tight sealed reservoir containing the volatile material; wherein, in use, the magnetic susceptor(s) is arranged to heat the material predominately by magnetic hysteresis when the magnetic susceptor(s) is at least partially positioned in the induced magnetic field generated, in use, when said alternating current is passed through the induction coil. Refills, devices and methods of use are also described.

Devices are known for emitting volatile liquids into an atmosphere. Inone known device, described in US Patent Publication No. 2002/0146243, adevice having a housing is provided with a container for the volatileliquid, a wick extending from the container and an annular electricalheater located in the vicinity of the distal end of the wick toaccelerate the evaporation of the volatile liquid from the wick. Thecontainer and wick are conventionally provided as a removable refill andthe device uses a positive temperature coefficient (PTC) thermistor asthe electrical heater. The device also has an electric plug by which itis plugged into a wall socket.

However, the heater must be run at a high temperature in order tosufficiently heat the volatile liquid within the wick. Further, theposition of the heater within the housing means that the heater heatsthe wick as well as the surrounding device housing which provides twodistinct drawbacks. Firstly, high levels of power consumption arerequired to get the electrical heater up to a satisfactory operatingtemperature to heat the wick to the temperature at which the volatileliquid can be emanated. Secondly, the mass of such an electrical heaterand the surrounding device housing typically holds residual heat for aprolonged period after power to the heater has ceased, as such if thereis an appetite to modify the operation of the device, particularly toaddress anti-habituation concerns associated with the emanated volatileliquid, such known devices are inherently slow to respond as removingpower from the heater does not appreciably slow the emanation rate dueto the residual heat.

Another known device can be found in International Publication No. WO2005/112510, which describes an induction heating apparatus for thedissemination of volatile liquids. The device has a base module and aseparate reservoir containing the volatile liquid. The base module hasan upwardly-projecting cylindrical portion within which is a primaryinduction coil. The base of the reservoir has a recess which fits overthe cylindrical portion of the base, around which is a secondaryinduction coil composed of a short-circuited wire coil. When current ispassed through the primary coil, the secondary coil heats up and thusheats the liquid to increase the rate of evaporation. However, thisdevice heats all of the volatile liquid in the reservoir, resulting in adevice which is slow to reach the ideal operating temperature andoperates with high levels of power consumption. Further, the device willcontinue to emit vapour after it has been switched off as the liquid inthe reservoir will retain considerable residual heat and will take quitesome time to cool. Furthermore, if the volatile liquid is a fragrance,heating the entire reservoir can degrade the quality of the fragranceover the life of the refill.

With the known devices as well as the Applicant's co-pendingapplications condensation in the device can occur due to the absence ofsufficient airflow therethrough and/or the device itself being coolduring operation, it is an object of the present invention to addresssuch drawbacks.

According to a first aspect of the present invention, there is providedan assembly for evaporating a volatile material, the assembly comprisinga device and a refill which are detachable from one another:

wherein the device comprises a magnetic induction coil configured tooperate with an alternating current passed therethrough at a frequencyof between substantially 20 KHz to substantially 500 KHz and one or morevolatile fluid emanation channels containing at least one piece of heatconducting, non-magnetic metal foil and/or deposited heat conducting,non-magnetic metal; and wherein the refill comprises at least onemagnetic susceptor having a coercivity of substantially 50 ampere/metre(H_(c)) to substantially 1500 ampere/metre (H_(c)) and a substantiallyliquid-tight sealed reservoir containing the volatile material; wherein,in use, the magnetic susceptor(s) is arranged to heat the materialpredominately by magnetic hysteresis when the magnetic susceptor(s) isat least partially positioned in the induced magnetic field generated,in use, when said alternating current is passed through the inductioncoil.

Preferably the one or more volatile fluid emanation channels is providedin the form of one or more chimneys or the like that are open at one endto receive the evaporated volatile fluid and open at their other end tothe environment surrounding the device. The chimney(s) may be rotatableand/or movable relative to the rest of the device and/or may be providedwith one or more holes and/or windows any or all of which may bearranged to promote airflow into the chimney and out into theenvironment surrounding the device.

The heat-conducting, non-magnetic metal may be selected from anysuitable non-ferrous metal. Preferably the heat-conducting, non-magneticmetal is selected from a metal readily available in sheet foil form.Particularly preferably the heat-conducting, non-magnetic metal isselected from one of aluminium, silver, gold, platinum, tungsten,magnesium or copper. Most preferably the heat-conducting, non-magneticmetal is aluminium, of which aluminium foil is the preferred form. Thealuminium sheet foil may be provided at any suitable thickness, althougha thickness of between substantially 8 μm to substantially 25 μm is mostpreferred. The deposited heat-conducting, non-magnetic metal ispreferably vacuum metalised deposited at a suitable thickness, althougha thickness of between substantially 0.1 μm to substantially 10 μm ispreferred.

The heat-conducting, non-magnetic metal will hereinafter be referred tosolely as “aluminium” for the sake of brevity but it is to be understoodthat the inventor does not intend for this to be limiting on theinvention disclosed herein, in other words, whilst aluminium is the mostpreferred heat-conducting, non-magnetic metal all subsequent referencesto “aluminium” are to be construed as relating to any suitablenon-ferrous metal that is heat-conducting and non-magnetic.

The aluminium may be provided in contact with the inner surface of the,or each, chimney in order to face the evaporated fluid.

The deployment of aluminium foil and/or deposited aluminium isconsidered advantageous as it can reduce condensation in operation ofthe device by imparting heat to the chimney(s) to reduce any temperaturedifferential between the evaporated fluid and said chimney(s) as well ascreating a temperature gradient in the device to promote air currentsthrough the device to improve the emanation of the evaporated fluid.

One key benefit of the deployment of aluminium foil and/or depositedaluminium compared to using either an additional magnetic susceptorwithin the device around the volatile fluid emanation channel(s) or evena standard PTC thermistor is that the aluminium foil and/or depositedaluminium will not heat up by any appreciable or effective amount whenexposed to the changing magnetic field induced by the induction coil asaluminium is non-magnetic and therefore is not capable of undergoingmagnetic hysteresis. Furthermore, aluminium is very poor at eddy currentheating. However, the aluminium in the device may heat up considerablywhen a refill containing a magnetic susceptor is attached to the devicesuch that the magnetic susceptor is within the induced magnetic field.Whilst not wishing to be bound by the following proposed hypothesis, theinventor of the present invention suspects that when the magneticsusceptor in the refill is present in the induced magnetic field thesusceptor has such an affinity for the induced magnetic field that itcan force the magnetic field to be drawn through the aluminium and indoing so causes the aluminium to heat up. By selecting to correctquantity and location for the aluminium it is possible for the aluminiumto heat to within approximately 5° C. of the susceptor temperature.

A further a key benefit of this arrangement is that the aluminiumcarries little mass and, therefore, has little ability to retain heat.Whereas the use of an additional magnetic susceptor within the devicearound the volatile fluid emanation channels or a standard PTCthermistor could be used to impart heat in the absence of a refill andfor a period of time after the alternating current is stopped, thealuminium would rapidly dispose of its residual heat thus ensuring thatthe device remains cool to the touch post-use and thus improving itssafety.

Preferably the refill is provided with a membrane to substantiallyliquid-tight seal the reservoir. The membrane may be a gas-permeablemembrane. Alternatively or additionally the membrane may include one ormore gas-permeable portions that can be exposed by the user of theassembly prior to insertion of the refill into the device.

The refill may be provided with a pierceable film to substantiallyliquid-tight seal the reservoir and the device may be provided with aperforating element which is configured to pierce the film when therefill is connected to the device. Alternatively or additionally, therefill may further comprise a lid which the perforating element may beconfigured to pierce when the refill is connected to the device.

The device may be provided with more than one perforating element topierce the refill in more than one location on the refill.

The evaporated material may emanate via a space formed between theperforating element and the pierced hole. However, preferably, the oreach perforating element is hollow. This provides one or more passagesfor evaporated material to emanate outside of the refill. By providingthe refill with a fluid-permeable membrane and/or a pierceable filmand/or lid the present invention allows different refills to beinterchangeably used in a quick, and mess-free, way. As the refills canbe so easily interchanged, the present invention is particularly suitedto the evaporation of small amounts of material. In this case, theproblems previously identified in relation to WO 2005/112510 are less ofan issue, because the amount of material being heated is small.Furthermore the presence of a fluid-permeable membrane and/or apierceable film and/or lid improves the safe operation of the assemblysince the susceptor(s) can be retained underneath same to prevent easeof finger access thereto, this being beneficial with the susceptor(s)become hot following use.

In some embodiments, the magnetic susceptor may be embedded within thereservoir. Enclosing the susceptor within the reservoir, rather thanhaving it exposed on an edge of the refill, minimises the potential forinjury as the susceptor is less accessible and therefore is less likelyto be accidently touched during use. Alternatively or additionally thereservoir may be lined in whole or in part by the magnetic susceptor. Asa further alternative or additional arrangement, the reservoir may becomposed in whole or in part of the magnetic susceptor.

Preferably, the magnetic susceptor is in the shape of a non-coiledstrip. This way, the susceptor is less prone to heating by eddy currentsand is instead designed to be heated predominately by hysteresis.

Preferably, where the volatile material is a volatile liquid and/or avolatile gel the refill may further comprise a volatile materialtransport means for transporting and storing some of the volatile liquidand/or gel.

The purpose of the volatile material transport means is to allow theevaporation of the volatile liquid and/or gel to be better controlled.Preferably the susceptor(s) is placed in contact with the volatilematerial transport means, and particularly preferably the susceptor(s)is wholly or partially embedded in the wick, such an arrangement meansthe heat emanating from the susceptor is largely contained within thevolatile material transport means, and is not transmitted to the liquidand/or gel contained in the reservoir.

In the context of the present invention the term volatile materialtransport means is used herein to refer to any physical fluid transportconduit that permits the fluid to flow away from the reservoir towardthe susceptor(s) without the assistance of gravity or powered means, inother words relying on capillary action, osmotic transfer, wickingaction or the like to transport the fluid. Therefore the volatilematerial transport means in the present invention may be a fibroussubstance such as a cellulose wick or the like or the volatile materialtransport means could be a porous substance such as ceramic wick or thelike. Alternatively the volatile material transport means may be a gelmatrix or the like, and in this arrangement the reservoir and thevolatile material transport means may be made from the same materialand/or may be substantially integral with each other.

If a volatile material transport means is used, the volatile materialtransport means may at least partially line the reservoir.

If a volatile material transport means is provided in the refill, thenit may be preferable for the susceptor(s) to be provided in directcontact therewith. In some embodiments the susceptor(s) may be at leastpartially embedded within the volatile material transport means.Alternatively or additionally, the susceptor(s) may surround a portionof the volatile material transport means. Most preferably however, thesusceptor(s) is entirely embedded within the volatile material transportmeans.

One advantage of enclosing/embedding the susceptor(s) entirely withinthe volatile material transport means is that the heat emitted from thesusceptor(s) is more effectively transferred to the adjacent volatilematerial in the volatile material transport means, and not to theentirety of the volatile material transport means to some or all of thereservoir. This is advantageous as where the volatile material is afragrance, a medicament, a pest control material or an activepharmaceutical Ingredient, heating the entire reservoir can degrade thequality of the material over the life of the refill which is clearlyundesirable.

Enclosing the susceptor(s) entirely within the volatile materialtransport means also minimises the potential for injury as the susceptoris less accessible and therefore is less likely to be accidently touchedduring use.

Since heat in the susceptor(s) is induced no electrical connection needsto pass through the reservoir to the susceptor(s) eliminating thepossibility of a resultant fluid leakage path.

As the susceptor(s) is magnetic the susceptor(s) is predominately heatedby magnetic hysteresis, and although some secondary eddy current heatingmay occur any eddy current heating is <50% of the heat generated in themagnetic susceptor(s), and preferably <40% of the heat generated in themagnetic susceptor(s) is from secondary eddy currents, and morepreferably <35% of the heat generated in the magnetic susceptor(s) isfrom secondary eddy currents, and most preferably less than <30% of theheat generated in the magnetic susceptor(s) is from secondary eddycurrents.

Hitherto the present invention the use of magnetic hysteresis as thepredominant mechanism of heating has not been explored, the explored“induction heating” mechanism is eddy current heating. In an eddycurrent heating system it is ultimately the resistance of the target(i.e. the susceptor) which is responsible for the dissipation of poweras heat. Preferably the electrical resistance of the target is low andthe external induction field induces many tiny voltages in the target.As the resistance is low, the current circulating in the target materialis huge, hence heat is produced. However the induced eddy current canalso be used to do other forms of work instead of just producing heat,such as charging batteries for example.

Efficient transfer of electrical current through an air gap or otherthermally insulating medium is fundamental to many applications ofinduction. The induced current can be used to produce resistive heatingvia eddy currents in a target on the opposite side of a thermallyinsulating material (e.g. air). Although induction heating applicationsare well known they have largely been applied to large white goods (e.g.Induction Hobs for cooking) or industrial processes (e.g. Furnaces). Inthese applications, despite the relatively high power levels andfrequencies needed, induction offers cost and efficiency advantages overmore traditional methods (e.g. resistive or joule heating) due to itsinherent ability to effectively cross insulating layers. However theassociated cost and complexity would be uneconomical where smalleramounts of heat are required or where such conditions do not exist.

One unwanted side effect of such eddy current induction processes isthat some secondary magnetic hysteresis occurs which imparts arelatively small amount of generated heat. Heat generated by magnetichysteresis is largely undesirable in transformers, power supplies andthe like. As such most of the research and development work has beenaround how to prevent this secondary effect which produces heat.

In magnetic hysteresis heating the resistance of the target (i.e.susceptor) is unimportant and any circulating eddy currents which mightoccur do not represent a significant contribution to heating of thetarget, as the mechanism is fundamentally different. During magnetichysteresis heating the magnetic domains within the target alignthemselves with the external field. When the polarity of the externalfield is reversed the magnetic domains reverse and realign themselveswith the new field direction and it is this continued motion of themagnetic domains that produces the heat. At low power and relatively lowfrequencies this mechanism can be made to dominate by selection of anappropriate target.

For example, copper is non-magnetic and when copper is used in a refillas a non-magnetic susceptor in place of the magnetic susceptor as calledfor in the present invention, when the alternating current passedthrough the induction coil in the device is 150 KHz the copper susceptormerely heats by approximately 4° C. which is due solely to Eddy currentheating. In contrast when the susceptor is magnetic and has a coercivitybetween substantially 50-1500_(c) then under the same induction coilconditions the magnetic susceptor heats to at least 10× greater than thenon-magnetic copper susceptor.

Preferably the magnetic susceptor(s) is made from at least one of thefollowing materials: cast iron (annealed); nickel; nickel-coated steel;cobalt; carbon steel (annealed) 1% C; constructional steel particularly(0.3% C, 1% Ni) and/or (0.4% C, 3% Ni, 1.5% Cr); cobalt-iron alloy,particularly Permendur 24 (24% Co) and Permendur 49 (49% Co); Heusleralloy (61% Cu, 26% Mn, 13% Al); tool steel; powdered iron (preferablyset in a resin base or the like to permit convenient shaping); ironfilings (preferably set in a resin base or the like to permit convenientshaping). Since the energy input to the assembly can be effectivelytargeted to heat the susceptor(s) within the induced magnetic field,only the susceptor(s) and the surrounding fluid in the volatile materialtransport means is heated rather than the energy being wasted as heatelsewhere in the refill and/or device as with the prior art assemblies.Further, as the susceptor(s) is a simple, low-cost component, it can becost efficiently provided as part of a refill.

In a preferred arrangement each refill may be provided with at least onesusceptor having heating characteristics which are optimised for thespecific fluid contained in the refill, without the need for userintervention or complex control. For instance, it may be preferable tomake the device as inexpensively as possible, therefore, one option tofacilitate inexpensive manufacture would be to provide the devicewithout any user-operable controls which permit a variation of itsoperating parameters such that the device operates in accordance with asingle set of operating parameters. In this arrangement the lengthand/or mass and/or composition of the susceptor(s) in the refill may bevaried to tune the heat achieved when the susceptor(s) is located withinthe induced magnetic field during use to the evaporation temperature ofthe volatile fluid. By way of example, where the volatile fluid is afragrance composition fragrances are generally composed of a combinationof top notes, middle notes and base notes. Top notes represent the mostvolatile part of the fragrance composition, these notes are usuallyperceived first by a human nose and include the “light” or “fresh”olfactive notes of the composition. The middle notes typically representthe “heart” of the mixture as they often provide the majority of thefragrance. The base notes are typically the least volatile part of themixture and includes the heaviest molecules such as the notes thatprovide “rich” or “deep” olfactive notes of the composition. Due totheir weight and size the base notes usually linger for the longestperiod. A fragrance mixture is typically made up of 10% top notes, 60%middle notes and 30% base notes. However, if it is desired to sell afragrance made up predominantly of top notes it would be possible todeploy a refill containing a susceptor that heats to a relatively lowtemperature to ensure that the highly volatile top notes do not flashoff to impart a user-desirable lifetime to the refill. Conversely if itis desired to sell a fragrance made up predominantly of base notes itwould be possible to deploy a refill containing a susceptor(s) thatheats to a relatively high temperature to ensure that the less volatilebase notes are evaporated at a satisfactory rate to be noticeable by theuser as well as imparting a user-desirable lifetime to the refill, i.e.a refill that will not last too long and risk clogging or blocking thevolatile material transport means.

Furthermore, this preferred arrangement would make it permissible tomarket refills containing markedly different formulations for use withthe same device. For instance, when evaporating fragrance formulationsthe preferred operating temperature may be in the order of 55-85° C.depending on the ratio of top, middle and base notes thereof, whereasfor a pest control formulation much higher operating temperatures aregenerally required, typically in the order of 120-140° C. Accordingly anassembly according to the present invention may provide a user with amuch simpler and inexpensive solution to emanate volatile fluids;simpler as the device can be left in situ and the desired refill may bechanged by the user without the user having to communicate to the devicethat the refill contains a different formulation; inexpensive as a userneed only purchase one device to emanate a wide variety of refillscontaining different formulations and the device need not have expensivenor complex refill recognition components to determine the deviceoperating parameters.

Although one option to facilitate inexpensive manufacture of a devicewould be to provide the device without any user-operable controls whichpermit a variation of its operating parameters, it may be preferable toprovide the device with basic user-operable controls which permitlimited variation of the operating parameters, say between 2-4predetermined operating parameters since some users may wish to changethe intensity of the evaporated volatile fluid depending of the type ofvolatile fluid, the size of the space the fluid is being emanated into,etc.

Alternatively where producing the device as inexpensively as possible isless of a concern the device may be provided with one or moreuser-controllable inputs to permit the user to alter one or moreoperating parameters of the device to provide the user with a multitudeof options to impart an emanation performance of the volatile fluid thatthey desire.

A further benefit of the assembly according to the present invention isthat the mass of the components being heated is lower than hithertoavailable assemblies such that there will be a reduced amount ofresidual heat in said heated components during use and once the inputenergy to the assembly stops. This is particularly advantageous forseveral reasons, firstly, this improves the safety of the assemblyduring operation since only a small proportion of the device and/orrefill will be heated thus making the assembly cool to the touch duringuse. Secondly, if there is the need to vary the emanation rate of thevolatile fluid it is possible to rapidly cease emanation of the volatilefluid by removing the input power to the induction coil and/or modifyingthe duty cycle to impart a rapid cool down of the susceptor. Forinstance, when concerned with addressing anti-habituation duringfragrance emanation it is necessary to allow a user's olfactivereceptors to become non-saturated with the particular fragrancemolecule(s) and this can only be achieved by ceasing the emanation ofthose fragrance molecule(s) and/or emanating a different fragrance. Theability of the device of the present invention to achieve rapidcool-down facilitates more rapid attenuation of the saturated olfactivereceptors.

To provide the device with a stable maximum operating temperature thesusceptor(s), may comprise a material with a stable Curie temperature,preferably less than 150° C. When the magnetic susceptor(s) is heatedbeyond this temperature, the susceptor(s) will become paramagnetic andno longer be susceptible to hysteresis heating until such time it coolsdown back below its Curie temperature. By selecting a magneticsusceptor(s) with a low and stable Curie temperature, it is possible toprevent the temperature of the volatile liquid in the volatile materialtransport means exceeding a predetermined level, even if for some reasonexcess power is supplied to the induction coil.

To ensure the heat generation within the susceptor(s) is as efficient aspossible, the susceptor(s) may be substantially completely locatedinside the induced magnetic field during the operation of the assembly.

In a preferred embodiment the refill is provided with a single magneticsusceptor.

Alternatively the refill may be provided with a more than one magneticsusceptor. In this arrangement by increasing the number of susceptors itis possible to increase the amount of heat generated within the samedevice operating parameters relative to when only a single susceptor ispresent. For example, where under fixed device operating parameters onemagnetic susceptor is heated to 80° C. it is surprisingly found that iftwo identical susceptors are in the induced field rather than bothheating to 80° C. they will both heat to 90° C. Furthermore, it issurprisingly found that if three identical susceptors are in the inducedfield rather than both heating to 80° C. or 90° C. they will both heatto 105° C. Whilst not wishing to be bound by the following proposedhypothesis, the inventor of the present invention suspects that thepresence of multiple susceptors within the induced field focuses thefield to the inside of the coil which decreases the area over which thefield is spread thus increasing the magnetic focus and efficiencythereof.

The volatile material may be one or more of a volatile solid, a volatileliquid, a volatile gel, a gas. Where a volatile solid is present saidsolid should have an mp>25° C. and a bp<150° C., and preferably anmp>50° C. and a bp<120° C., examples include crystals of menthol orcamphor. The volatile solids could be formed to be adjacent thesusceptor or imbedded in a mat or a matrix to be located adjacent thesusceptor. Preferably the volatile material is a volatile liquid and/ora volatile gel.

In some embodiments, the device may further comprise a control unit tocontrol the operation of the induction coil. In such an embodiment, thedevice may further comprise a feedback coil configured to interact witha magnetic field generated by the induction coil. Preferably thefeedback coil is provided in the form of feedback windings turned aroundthe induction coil, most preferably about 12 windings around the primarycoil. In this arrangement the control unit may be configured to processan output from the feedback coil and, from this output, vary one or moreoperating parameters of the induction coil. The feedback coil ispreferably configured to be capable of changing its output, in use, whena susceptor(s) is within the magnetic field of the induction coil.

Preferably the feedback coil in may be configured, in use, to change itsoutput when one property of a susceptor is changed from refill torefill, for example if the shape or mass or material or surface area ofthe susceptor changes. The control unit may then be configured tointerpret the change in output from the feedback coil to determine whattype of refill is within the magnetic field of the induction coil, andfrom this, automatically vary a property of the induction coil to applythe appropriate heating regime to each particular refill.

To ensure the control unit is as simple as possible, thus as inexpensiveas possible, the assembly is preferably configured such that thefeedback coil only has to change its output in response to a change of asingle property of the susceptor from refill to refill, therefore, it ispreferred for refills configured to be used with such a device to havethree of the following susceptor properties fixed and one of thefollowing susceptor properties variable for detection of this varianceby the feedback coil, wherein said susceptor properties are: shape;mass; material and surface area.

The provision of a feedback coil could also be used to prevent thesusceptor(s) from getting too hot during use. As the susceptor(s) getshot, the output from the feedback coil changes. The control unit couldbe configured to interpret a high temperature of the susceptor(s) basedon this output, and from this, automatically vary a property of theinduction coil to cool the susceptor.

A further use for the feedback coil the device could be to ensure thatthe device is operating as efficiently as possible, in this preferredarrangement the control unit monitors the output of the feedback coil toalter the duty cycle as required to ensure the current supplied throughthe induction coil is optimised to the particular susceptor(s) inproximity with the induction coil.

Examples of the device operating parameters which may be varied by thecontrol unit may be the maximum amplitude, the frequency, or the dutycycle of the current being passed through the induction coil.

Alternatively or additionally, the device may be provided withmechanical or electromechanical means that are operable by the controlunit to physically move the refill such that the susceptor is movedrelative to the induced magnetic field of the induction coil.Alternatively or additionally, the device may be provided withmechanical or electromechanical means that are operable by the controlunit to physically move the induction coil within the device housingsuch that the induced magnetic field is moved relative to the susceptorin the refill.

By configuring the assembly such that the alternating current passedthrough the induction coil has a frequency greater than 20 KHz theinduction coil may more effectively heat up the susceptor by magnetichysteresis. Preferably, the alternating current passed through theinduction coil may be set at a frequency greater than 100 KHz, and morepreferably set at a frequency of 150 KHz.

In some embodiments, the device may accommodate more than one refillthus providing the assembly with multiple reservoirs each having theirown susceptor.

The presence of the multiple reservoirs allows more than one type ofvolatile fluid to be dispensed by the device by the single inductioncoil simultaneously.

Alternatively the device may be provided with more than one inductioncoil, each induction coil being associated with a separate refillwhereby, in use, the induced magnetic field from one induction coilsurrounds the susceptor(s) in only one refill, this may permit alternateemanation of the volatile fluid from each respective refill, this may beespecially preferably when the volatile fluids are fragrances.

In some embodiments, the device may further comprise alignment meansprovided on either of the device or the refill which is configured toalign the refill with the device.

The purpose of this alignment means is to ensure that the susceptor isappropriately positioned with respect to the induction coil.

In other embodiments, the device may further comprise an additionalmagnetic susceptor configured to heat an area around the induction coil.

The benefit of this additional susceptor is to ensure that thecomponents around the induction coil are appropriately heated, forinstance the core of the induction coil or members which support theinduction coil, such to avoid any volatile material which evaporatesfrom condensating onto these components.

According to a second aspect of the present invention, there is providedtherefore a device for evaporating a volatile material from a detachablerefill of volatile fluid comprising a reservoir for the volatilematerial and at least one magnetic susceptor having a coercivity ofsubstantially 50 ampere/metre (H_(c)) to substantially 1500 ampere/metre(H_(c)); wherein the device comprises a magnetic induction coilconfigured to operate with an alternating current passed therethrough ata frequency of between substantially 20 KHz to substantially 500 KHz toinduce a magnetic field and one or more volatile fluid emanationchannels containing at least one piece of heat-conducting, non-magneticmetal foil and/or deposited heat-conducting, non-magnetic metal.

According to a third aspect of the present invention, there is provideda method for evaporating a volatile material, comprising the steps oflocating a refill comprising a reservoir for the volatile material andat least one magnetic susceptor having a coercivity of substantially 50ampere/metre (H_(c)) to substantially 1500 ampere/metre (H_(c)) in adevice comprising a magnetic induction coil configured to operate withan alternating current passed therethrough at a frequency of betweensubstantially 20 KHz to substantially 500 KHz to induce a magnetic fieldand one or more volatile fluid emanation channels containing at leastone piece of heat-conducting, non-magnetic metal foil and/or depositedheat-conducting, non-magnetic metal;

generating a magnetic field through said induction coil by passing an ACcurrent at a frequency of between substantially 20 KHz to substantially500 KHz therethrough;

said locating of the refill in the device being such that the at leastone magnetic susceptor is at least partially within the generatedmagnetic field;

and evaporating the volatile material by said at least one magneticsusceptor being heated predominately by magnetic hysteresis induced bythe changing magnetic field from the induction coil to evaporate thevolatile material and by said at least one piece of heat-conducting,non-magnetic metal foil and/or deposited heat-conducting, non-magneticmetal heating to resist condensation of the evaporated fluid within thedevice.

The device may further comprise a control unit and/or a feedback coiland the method may comprise the control unit controlling the operationof the induction coil. The method may further comprise the control unitprocessing an output from the feedback coil and, from this output,varying one or more operating parameters of the induction coil.

The feedback coil may be configured, in use, to change its output whenone property of a susceptor is changed from refill to refill, forexample if the shape or mass or material or surface area of thesusceptor changes. The method may further comprise the control unitbeing configured to interpret the change in output from the feedbackcoil to determine what type of refill is within the magnetic field ofthe induction coil, and from this, automatically vary a property of theinduction coil to apply the appropriate heating regime to eachparticular refill.

As the susceptor(s) gets hot, the output from the feedback coil changes.The method may further comprise the control unit interpreting the outputof the feedback coil to determine a high temperature of the susceptor(s)and automatically varying a property of the induction coil to cool thesusceptor.

A further use for the feedback coil in the device could be to ensurethat the device is operating as efficiently as possible. The method mayfurther comprise the control unit monitoring the output of the feedbackcoil to alter the duty cycle as required to ensure the current suppliedthrough the induction coil is optimised to the particular susceptor(s)in proximity with the induction coil.

The method may comprise the control unit may comprises the steps of thecontrol unit varying one or more of the operating parameters of theinduction coil by varying one or more of: the maximum amplitude; thefrequency; the duty cycle.

The method preferably includes the step of the device being operated topass an alternating current through the induction coil with a frequencygreater than 20 KHz to more effectively heat up the susceptor bymagnetic hysteresis, and preferably greater than 100 KHz, and morepreferably at a frequency of 150 KHz.

Preferably, substantially all of the material in the reservoir isconfigured to be evaporated within 5 hours of continuous actuation ofthe induction coil.

More preferably, substantially all of the material in the reservoir isconfigured to be evaporated within 3 hours of continuous actuation ofthe induction coil.

The invention will now be described, by example only, with reference tothe accompanying drawings in which:

FIG. 1 shows a block diagram of an embodiment of the present invention.

FIG. 2 shows in more detail one example of the electronic circuitry usedin the embodiment shown in FIG. 1.

FIG. 3 shows in more detail a further example of the electroniccircuitry used in the embodiment shown in FIG. 1.

FIGS. 4A-4C show an example layout of the invention.

FIGS. 5A-5C show exemplary designs for the interior of the refill shownin FIGS. 4A-4C.

FIG. 6 shows hysteresis loops for two different susceptor materials.

FIG. 1 shows a device 1 and a refill 2. The device 1 comprises a powersource 101 connected to electronic circuitry 102. Making up a part ofthis electronic circuitry is an induction coil 103 and an optionalfeedback coil 104.

The refill 2 is a separate component to the device 1. The refill 2comprises a reservoir 201, which holds volatile material 202. The refill2 also comprises a susceptor 204, and an optional volatile materialtransport means 203, illustrated here in the form of a wick.

Where a wick 203 is present, the susceptor should be preferably in, orat least partially in, the wick. The wick 203 should extend beyond thereservoir 201 so that the material 205 which evaporates from the wick203 can pass to the exterior of both the device 1 and the refill 2.

The power source 101 of the device 1 may for example be a connection toa mains supply, a connection to a USB docking station, or a battery.

The circuit diagrams shown in FIGS. 2 and 3 are examples ofself-resonant/self-oscillating zero voltage switched (ZVS) convertercircuits. Such circuits are well known in the art.

The ZVS circuits shown are configured to provide a high frequencymagnetic field across an induction coil L2 (approximately 200 KHz). InFIG. 2, the circuit is located between a line supply L_(s) and a groundconnection L_(G). Connected to the line supply L_(s) is the power source101, which provides the line supply L_(s) with AC current. On the linesupply L_(s) is a diode D1. The circuitry also comprises the feedbackcoil 104, the induction coil 103, three capacitors C2;C3;C4, tworesistors R1;R3, and two transistors Q2;Q3.

The component layout in FIG. 3 is similar to that of FIG. 2, except forthe addition of a system microcontroller unit (MCU) or control unit,with its own power supply which feeds off the line supply L_(s), andwhich is adapted from the line supply L_(s) by conventional powerstepping electronics which are not shown, an additional resistor R1, anadditional capacitor C1, and first and second extra diodes D2 and D3.Preferably the additional capacitor C1 is polarised, and preferably thesecond additional diode D3 is a Schottky diode. The purpose of the MCUin FIG. 3 is to control the duty cycle of the ZVS converter, and hencethe power being delivered through the induction coil 103.

In each of FIGS. 2 and 3, the capacitor C4 is the resonating capacitorof the ZVS circuit. The high frequency voltage present at a collector Q3is coupled by capacitor C4 to a rectifying and regulating networkcomprising diodes D3 and D2, and the capacitor C1. In the case of FIG.3, the smoothed and regulated voltage present across capacitor C1 isused to power low voltage sections of the circuit including the MCU.

Operation of the invention as shown in FIGS. 1-3 will now be described.

Prior to use, the power source 101 of the device 1 must be fully chargedor connected. Once the device 1 is switched on, the electronic circuitry102 of the device 1 is then configured to pass an AC current through theinduction coil 103. The circuitry 102 may be configured to continuallypass an AC current through the induction coil 103, or alternatively maybe configured to only pass AC current through the induction coil 103when the refill 2 containing the susceptor 204 is located near theinduction coil 103, as will be discussed.

A refill 2 as shown in FIG. 1 is connected to or docked with the device1. To hold the refill 2 in place on the device 1, a fastening means,clip, or cradle may be provided on the device 1, as is shown for examplein FIGS. 4A-4C. However the refill 2 is connected to the device 1, themain requirement is that the susceptor 204 inside the refill 2 is closeenough to be heated by the induction coil 103, and to interact with theoptional feedback coil 104, located on the device 1, as will bediscussed.

Once the refill 2 is engaged with the device 1, the susceptor 204 of therefill 2, which is positioned within the magnetic field of the inductioncoil 103will begin to heat up by predominately magnetic hysteresisheating and possibly to a minor degree also by eddy current heating.

As the susceptor 204 heats up, volatile material 202 around thesusceptor 204 also starts to heat up and vaporise for dispersion tooutside the refill 2.

To control how much volatile material 202 is dispersed at any giventime, the electronic circuitry 102 from the device 1, in particular theMCU, can control the amount of current flowing through the inductioncoil 103, and hence control the amount of heating occurring in thesusceptor 204. The current flowing through the induction coil 103 can bevaried for example by increasing the duty cycle of the circuit, or byincreasing the maximum current flowing through the induction coil 103.Such control can be either by external human input, for example by anend user via a switch or dial, or preferably by the MCU in response toan output from a feedback coil 104 provided in the electronic circuitry102, as is discussed below.

If a feedback coil 104 is provided, when current is flowing through theinduction coil 103, the feedback coil 104 will pick up the magneticfield being emitted from the induction coil 103. When a susceptor 204contained in a refill 2 is inserted into this magnetic field, themagnetic field will become distorted, depending on the shape of thesusceptor, and so the signal being picked up from the feedback coil 104will change. By electrically connecting the MCU to the feedback coil104, the MCU can be configured to interpret the signal received from thefeedback coil 104, and from this interpret what type or shape ofsusceptor 204 is positioned near the device 1, if any.

The feedback coil 104 can also be used as a power control means toprevent the susceptor 204 from getting too hot. As the susceptor heatsup during operation, its effect on the magnetic field generated by theinduction coil 103 changes. By electrically connecting the MCU to thefeedback coil 104, the MCU can be configured to interpret the signalreceived from the feedback coil 104, and from this interpret thetemperature of the susceptor 204. The MCU can then control the amount ofcurrent being passed through the induction coil 103.

Another use for the output from the feedback coil 104 by the MCU is formonitoring the form of power being supplied by the electronic circuitry.By sampling the output signal from the feedback coil 104, the MCU can beconfigured to vary the properties of the electronic circuitry to ensurethat the alternating current being passed through the induction coil 103is matched to the particular susceptor 204 in proximity with theinduction coil 103.

If no MCU or feedback coil 104 is present in the electronics of theevaporation device, the device operates at a predetermined power leveland operates in either an “on” or “off” state.

An example design of both the device 1 and refill 2 is shown in FIGS.4A-4C. The configuration of both the device 1 and refill 2 is largelydependent on the induction coil 103 being able to efficiently heat thesusceptor 204, and if a feedback coil 104 is present, allowing this coilto interact with the magnetic fields generated by the induction coil103. In the case of FIGS. 4A-4C, the induction coil 103 is tubular inshape and is located such that once the refill 2 is connected with thedevice 1, the susceptor 204 fits inside the induction coil 103. Althoughnot shown in FIGS. 4A-4C, where a feedback coil 104 is also present,this could be placed in a concentric type arrangement in or around theinduction coil 103.

The refill 2 comprises a material reservoir 201 containing volatilematerial 202. This material is evaporated by heat from a susceptor 204.The refill 2 also comprises a cover 206 which can be perforated.

The device 1 of the example shown in FIGS. 4A-4C comprises tube likeperforating elements 105 which are configured to pierce the cover 206 ofthe refill 2 during operation of the evaporation device. The inductioncoil 103 on the base element 1 is located to conform to the outer shapeof the refill 2.

To operate the embodiment shown in FIG. 4A-4C, a user places the refill2 into the device 1 such that the susceptor 204 therein can interactwith the induction coil 103 of the device 1. To aid with placing therefill 2 in the correct orientation, an alignment feature (not shown)could be provided on the refill 2 which locates with a correspondingfeature on the device 1.

The user then closes the lid of the device 1 to cause the perforatingelement 105 to pierce into the cover 206. The induction coil 103 thenheats the susceptor 204 of the refill 2 as previously described, causingvolatile material 202 to evaporate and flow out through the perforatingelements 105.

To reduce condensation within the device 1 a layer of aluminium foil islocated on an inner surface of the perforating elements 105 that forms achimney to direct evaporated fluid to the exterior of the device 1. Thealuminium foil 205 heats up, it is suspected, by the susceptor 204having a sufficient affinity for the induced magnetic field that itforces the magnetic field through the aluminium foil 205 which resultsin the foil 205 heating up thus to within 5° C. of the susceptor 204temperature. This heating of the aluminium foil 205 reduces thelikelihood for condensation within the device 1 and also promotesairflow therethrough as it creates a thermal gradient between thechimney and the air surrounding the device 1.

It is possible that the volatile material 202 in the embodiment of FIGS.4A-4C be in the form of a gel.

As an optional safety feature to the design as shown in FIGS. 4A-4C, theperforating element 105 may be configured to be made inaccessible whenthe device is not in use.

FIGS. 5A-5C show three exemplary cross sections for the interior of therefill 2.

FIG. 5A shows a first design where no wick 203 is used. In this design,the susceptor 204 directly heats the volatile material 202 in thereservoir 201. The susceptor may be positioned in or on the reservoir.Preferably the susceptor 204 should be designed and positioned so as toensure that substantially all the volatile material in the refill 2 canbe evaporated.

Although the susceptor 204 shown in FIG. 5A is shown as being a separatecomponent to the material reservoir 201, this need not necessarily bethe case as the wall of the material reservoir 201 could instead act asthe susceptor. In this situation, when an alternating current is passedthrough the induction coil 103, the whole reservoir 201 around thevolatile material 202 would heat up. In this situation, it would benecessary to ensure that a user could not touch the reservoir 201 of therefill 2 whilst volatile material 202 evaporates to ensure that they arenot injured.

An alternate design for the refill 2 is shown in FIG. 5B which uses awick 203. In this case, the wick is shaped to sit in the bottom of thereservoir 201, and is pre-saturated with volatile material 202. Thesusceptor 204 is preferably placed within the wick 203. When thesusceptor 204 is heated by the induction coil 103, the volatile material202 near the susceptor starts to evaporate from the wick 203. As thisvolatile material evaporates, volatile material 202 located further awayfrom the susceptor 204 diffuses towards it through capillary action inthe wick 203.

A third design for the refill 2 is shown in FIG. 5C which is a hybrid ofthe designs shown in FIGS. 5A and 5B. In this design, at least a portionof the wick 203 extends above the volatile material 202 in the reservoir201. As material evaporates from the wick 203, new volatile materialenters the wick 203 from the reservoir 201. The new volatile materialdiffuses towards the susceptor 204 through capillary action in the wick203 as previously described.

Although only one susceptor 204 is shown in FIGS. 4A-5C, it could bethat more than one susceptor 204 is used.

Exemplary shapes for each susceptor 204 could be a band running down alength of the reservoir 201 and/or the wick 203, or a ring passingaround it. Other shapes could also be used depending on how the volatilematerial 202 in the reservoir 201 is intended to be heated, anddepending on where the induction coil 103 is positioned in the device 1.

It will be appreciated that the designs shown in FIGS. 4A-5C could beadapted to allow the accommodation of more than one refill 2. Forexample, extra ports could be provided on the device 1 to allow theconnection of additional refills 2. Each port on the device 1 could beprovided with its own induction coil 103 such that the material 202contained in each refill 2 could be heated independently of the materialcontained in the other refills 2. Alternatively, all the refills 2 couldbe selectively heated by a single induction coil 103 located on thedevice 1, using conventional time switching circuitry. Irrespective ofthe number of induction coils 103 or number of refills 2 used, theprinciple of operation would be the same as previously described.

Ideally the magentic material for the magnetic susceptor should have ahigh hysteresis loss so that when it is repeatedly magnetised anddemagnetised by an external magnetic field a relatively high proportionof the external field energy is converted into heat. The magneticproperties exhibited by such a magnetic material may be represented by aplot of flux density (B) against magnetic field strength (H) as shown inFIG. 6. Materials having relatively low hysteresis losses are typifiedby the solid hysteresis loop which has a small area whilst materialshaving relatively high hysteresis losses are typified by the dottedhysteresis loop which has a high area. The proportion of the externalmagnetic field energy that is converted into heat by the susceptor foreach magnetic cycle is proportional to the area of the hysteresis loopcorresponding to the particular magnetic material. Accordingly magneticmaterials having small area hysteresis loops generate less heat whensubjected to a given alternating magnetic field and function poorly assusceptor materials. Conversely magnetic materials having large areahysteresis loops generate more heat when subjected to the samealternating magnetic field and function well as susceptor materials. Thearea of the hysteresis loop of a magnetic material is proportional toits coercivity so that a material having a high coercivity may beparticularly suitable for use as a susceptor. Such a material shouldhave a coercivity in the range of 50-1500 ampere per metre (H_(c)).

There is an upper range to the coercivity to guard against anexcessively high coercivity in order that external alternating magneticfields may readily bring about the necessary magnetic flux reversals inthe material thus preventing fine control of the heating performance viamagnetic hysteresis. Such materials are known as magnetically softmaterials and are distinguished thereby from the very high coercivitymagnetically hard materials which are typically used in permanent magnetapplications.

1. A volatile material evaporating assembly, the assembly comprising adevice and a refill which are detachable from one another: wherein thedevice comprises a magnetic induction coil operable with an alternatingcurrent passed therethrough at a frequency of between about 20 KHz andabout 500 KHz and one or more volatile fluid emanation channelscontaining at least one piece of heat-conducting, non-magnetic metalfoil and/or deposited heat-conducting, non-magnetic metal; and whereinthe refill comprises at least one magnetic susceptor having a coercivityof between about 50 ampere/metre (H_(c)) and about 1500 ampere/metre(H_(c)) and a substantially liquid-tight sealed reservoir containing thevolatile material; wherein, the at least one magnetic susceptor operatesto heat the material predominately by magnetic hysteresis when the atleast one magnetic susceptor is at least partially positioned in theinduced magnetic field generated, when said alternating current ispassed through the induction coil.
 2. An assembly according to claim 1,wherein the one or more volatile fluid emanation channels is provided inthe form of one or more chimneys or the like that are open at one end toreceive the evaporated volatile fluid and open at their other end to theenvironment surrounding the device.
 3. An assembly according to claim 2,wherein the one or more chimneys are rotatable and/or movable relativeto the rest of the device.
 4. An assembly according to claim 2, whereinthe one or more chimneys are provided with one or more holes and/orwindows any or all of which are arranged to promote airflow into thechimney and out into the environment surrounding the device.
 5. Anassembly according to claim 1, wherein the heat-conducting, nonmagneticmetal is selected from the group consisting of: aluminium, silver, gold,platinum, tungsten, magnesium and copper.
 6. An assembly according toclaim 1, wherein the heat-conducting, non-magnetic metal is aluminium,aluminium foil.
 7. An assembly according to claim 1, wherein theheat-conducting, nonmagnetic metal foil is provided in the form of sheetfoil of a thickness of between about 8 μm and about 25 μm.
 8. Anassembly according to claim 1, wherein the deposited heat-conducting,non-magnetic metal is provided as a vacuum metalised deposit having athickness of between about 0.1 μm and about 10 μm.
 9. An assemblyaccording to claim 2 wherein the heat-conducting, non-magnetic metal isadapted to be in contact with the inner surface of the at least onechimney and faces the evaporated fluid.
 10. An assembly according toclaim 1, wherein secondary eddy current heating provides <50% of theheat generated in the at least one magnetic susceptor.
 11. An assemblyaccording to claim 1, wherein the at least one magnetic susceptorcomprises at least one of the following materials: cast iron ; nickel;nickel-coated steel; cobalt; carbon steel 1% C; constructional steelcobalt-iron alloy Heusler alloy; tool steel; powdered iron; and ironfilings.
 12. An assembly according to claim 1, wherein the at least onesusceptor comprises a material with a stable Curie temperature.
 13. Avolatile material evaporating device operable to evaporate a volatilematerial from a detachable refill comprising a reservoir containing avolatile material and at least one magnetic susceptor having acoercivity of about 50 ampere/metre (H_(c)) to about 1500 ampere/metre(H_(c)); wherein the device comprises a magnetic induction coil operablewith an alternating current passable therethrough at a frequency ofbetween about 20 KHz and about 500 KHz which induces a magnetic fieldand one or more volatile fluid emanation channels containing at leastone piece of heat-conducting, non-magnetic metal foil and/or depositedheat-conducting, nonmagnetic metal.
 14. A device according to claim 13,wherein the one or more volatile fluid emanation channels is provided inthe form of one or more chimneys or the like that are open at one end toreceive the evaporated volatile fluid and open at their other end to theenvironment surrounding the device.
 15. A device according to claim 14,wherein the one or more chimneys are rotatable any/or movable relativeto the rest of the device.
 16. A device according to claim 14, whereinthe one or more chimenys are provided with one or more holes and/orwindows any or all of which are arranged to promote airflow into thechimney and out into the environment surrounding the device.
 17. Adevice according to claim 13, wherein the heat-conducting, non-magneticmetal is selected from the group consisting of: aluminium, silver, gold,platinum, tungsten, magnesium or copper.
 18. A device according to claim13, wherein the heat-conducting, non-magnetic metal is aluminium, oraluminium foil.
 19. A device according to claim 13, wherein theheat-conducting, non-magnetic metal foil is provided in the form ofsheet foil of a thickness of between about 8 μm and 25 μm.
 20. A deviceaccording to claim 13, wherein the deposited heat-conducting,nonmagnetic metal is provided as a vacuum metalised having a thicknessof between about 0.1 μm and about 10 μm.
 21. A device according to claim14 wherein the heat-conducting, non-magnetic metal is provided incontact with the inner surface of the one or more chimneys and faces theevaporated fluid.
 22. A method for evaporating a volatile material,comprising the steps of: locating a refill comprising a reservoircontaining the volatile material and at least one magnetic susceptorhaving a coercivity of between about 50 ampere/metre (H_(c)) and about1500 ampere/metre (H_(c)) in a device comprising a magnetic inductioncoil operable with an alternating current passing therethrough at afrequency of between about 20 KHz and about 500 KHz to which induces amagnetic field and one or more volatile fluid emanation channelscontaining at least one piece of heat-conducting, non-magnetic metalfoil and/or deposited heat-conducting, nonmagnetic metal; generating amagnetic field through said induction coil by passing an AC current at afrequency of between about 20 KHz and about 500 KHz therethrough; saidlocating of the refill in the device being such that the at least onemagnetic susceptor is at least partially within the generated magneticfield; and evaporating the volatile material by said at least onemagnetic susceptor heated predominately by magnetic hysteresis inducedby the changing magnetic field from the induction coil to evaporate thevolatile material and by said at least one piece of heat-conducting,non-magnetic metal foil and/or deposited heat-conducting, non-magneticmetal heating which resists condensation of the evaporated fluid withinthe device.